=SUM(INDEX(1:1,1,COLUMN()-12):INDEX(1:1,1,COLUMN()-1))

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HTH

Bob Phillips

(replace xxxx in the email address with gmail if mailing direct)

"Mopechicken" wrote in message
...
I need to sum the preceding 12 cells in a row within excel - regardless of
the fact that some columns will be added in front of this cell with the
formula. I want the formula to "float" just not sure how to accomplish
it?